Reactor incorporating a heat exchanger

ABSTRACT

A reactor containing a heat exchanger is disclosed, which can be operated with co-current or counter-current flow. Also disclosed is a system that includes a reactor having a reformer and a vaporizer, a fuel supply, and a water supply. The reactor includes a source of combustion gas, a reformer operative to receive reformate, and a vaporizer operative to receive water. The reformer and vaporizer each include a stack assembly formed by a combination of separator shims and channel shims. The separator shims and channel shims are stacked in a regular pattern to form two sets of channels within the stack assembly. One set of channels will have vertical passageways at either end and a horizontal flowpath between them, while the other set of channels has only a horizontal flowpath.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/205,827, filed Mar. 12, 2014, now U.S. Pat. No. 9,834,441, whichclaims priority to U.S. Provisional Patent Application Ser. No.61/777,935, filed Mar. 12, 2013. The entirety of that application ishereby fully incorporated by reference herein.

BACKGROUND

The present disclosure relates to heat exchangers, systems, methods, anddevices for performing an energy intensive reaction, either exothermicor endothermic. The devices disclosed herein are particularly applicableto steam/hydrocarbon reforming, and can also be used in otherapplications. Generally, the system may be used to generate electricityby reforming a mixture of steam and hydrocarbon fuel in a fuel processorthat outputs hydrogen gas to a fuel cell. The method for forming theheat exchanger may include diffusion bonding of a stack of alternatingshims of appropriate design. The heat exchanger can be used in a reactorusable in connection with different types of fuel cells, e.g.,proton-exchange membrane fuel cell (PEMFC) and solid oxide fuel cell(SOFC), to generate electricity in an effective and low cost manner. Thedevice may also include a counter-flow configuration and/or lateral heattransfer between reactant gases and combustion gases to enhance thermalflow and overall efficiency.

Fuel cells serve as a popular alternative to other energy sources due totheir high efficiency and relatively benign reaction byproducts. Fuelcells produce electricity through an electrochemical reaction between afuel input and an oxidant. Many fuel cells to date have been designed touse hydrogen as the fuel input. However, storing large quantities ofneeded hydrogen gas for the fuel cell has often proved to beimpracticable. To address the known disadvantages of hydrogen gasstorage, systems to produce hydrogen gas on-demand have been developed.

One type of fuel processor system generates hydrogen on-demand byreforming a hydrocarbon fuel into usable hydrogen. The hydrocarbon fuelsused by this fuel processor system are easier to store using existingstorage infrastructure relative to hydrogen gas. Reforming hydrocarbonfuel into hydrogen gas requires steam to oxidize the hydrocarbon fuelinto carbon monoxide (CO) and hydrogen (H₂), typically in the presenceof a catalyst. Steam reforming is also a strongly endothermic reactionthat must be performed at high temperature to improve the yield ofhydrogen gas produced. Therefore, effective thermal management betweenreactant gas and combustion gas flowing within a fuel processor systemis crucial to maintain reaction temperatures.

Current fuel processor systems include a fuel processor which receives areformate input (steam and hydrocarbon fuel reactant mixture) andproduces a syngas output (hydrogen and carbon monoxide). In some knownsystems, the hot combustion gas flows in channels that are perpendicular(i.e. at a 90° angle) to the channels through which the reformate inputflows, a configuration referred to as a cross-flow panel configuration.In other known systems, the hot combustion gas flows in the samedirection as reformate input along parallel channels, also known asco-flow. In yet other known systems, the hot combustion gas flows in anopposite direction to reformate input along parallel channels, aconfiguration referred to as counter-flow. Counter-flow may be apreferred method for reactions having a large temperature differentialbetween hot combustion gas and reactant gas. Counter-flow is believed tobe more advantageous than a cross-flow or co-flow configuration becauseit enables more efficient lateral heat transfer between reactant gasesflowing within reaction channels and combustion gases flowing withincombustion channels.

Current heat exchangers present many limitations, including highfabrication costs, large size, and sensitivity to carbon formation.These heat exchangers are also expensive to make. One reason for thehigh fabrication expense is the number of high-skilled welds, bothinternal and external, that are required. For example, pressure weldsare currently used to fabricate fuel processors. A large number ofhigh-skilled pressure welds are required to assemble reactor panels intopanel sets and then panel assemblies.

It would be desirable to provide heat exchangers that are easier tomake, less costly, and less sensitive to carbon formation. These heatexchangers may provide lateral heat transfer between reactant gases andcombustion gases to enhance thermal flow and overall efficiency. Theheat exchangers may be used as fuel processors for steam reforming orsimilar reactions.

BRIEF DESCRIPTION

The present disclosure relates to heat exchangers, systems, methods, anddevices for transferring heat between two different flowpaths. Suchdevices can be useful in fuel reformation or other similar reactions.The present disclosure describes methods for forming stack assembliesemploying diffusion bonding of simple shims as opposed to welding orbonding of finely-detailed shims as has been practiced previously. Thesimple shims can be designed for self-fixturing, which simplifies thebonding process and reduces costs. The configuration described mayfurther allow for increased total catalyst loading for a reactor ofgiven size. A shim design based on simple geometric scaling can cut thecost of traditional fabrication methods employing numerous high-skilledwelds and fine-detailed shims. A reactor can include stacks of reformerand vaporizer shims arranged in a compact, linear configuration. Thecompact and low-cost nature of the device permits the device to be usedfor commercial applications or alternatively scaled up for industrialapplications. For example, the reactor can be used as a fuel processorfor fuel reformation. Heat transfer in the reactor can occur via co-flowor counter-flow configurations.

Disclosed in embodiments is a heat exchanger (800, 110, 510, 610, 590),comprising a first channel, a second channel, and a fin. The firstchannel (810, 134, 135, 138, 139, 151) has a flowpath, a first wall(805), a second wall (832) opposite the first wall, an inlet manifold(812, 124, 120, 620, 640) at a first end, and a outlet manifold (814,128, 122, 628, 648) at a second opposite end. The inlet manifold and theoutlet manifold are orthogonal to the flowpath of the first channel Thesecond channel (820, 133, 137, 153) has a flowpath parallel to thehorizontal flow path of the first channel, the first channel and thesecond channel being separated by the first wall. The fin (845, 341,361, 556) extends from the second channel into the first channel, thefin passing through the first wall (805) and extending to the secondwall (832).

In embodiments, the first channel (810, 134, 135, 138, 139, 151) has aplurality of micro-channels (811) and the second channel (820, 133, 137,153) has a plurality of micro-channels (821). The ratio of a firstmicro-channel width (836) to a first micro-channel height (834) is from2:1 to 20:1.

The heat exchanger can be formed from a channel shim (830, 344, 364,540) and a separator shim (840, 342, 362, 550), wherein the channel shimdefines the first channel, wherein the separator shim includes the fin.In some embodiments, the ratio of a channel shim height (834) to aseparator shim height (844) may be from 0.125 to 8, including from 0.5to 2.

The channel shim (830, 344, 364, 540) may comprise at least onemicro-channel (346, 348, 365, 547, 548) extending from a first end (541)of the channel shim to a second end (542) of the channel shim. Themicro-channel (346, 348, 365) may further comprises a mixing manifold(347). The separator shim (840, 342, 362) may further comprise slots(386, 432, 434) that align with the micro-channel of the channel shim.

In some embodiments, the micro-channel (365) of the channel shim (364)can be formed from two longitudinal walls (366) joined together by atleast one transverse support (367), the micro-channel thus beingseparated into a series of chambers, wherein the chamber at a first endof the micro-channel is shorter in length than the other chambers. Thetransverse supports also provide cross-support to the longitudinal wallsto aid in maintaining their shape until they are bonded together.

In other embodiments, the channel shim (364, 540) has only one notch(369, 549) on an end. The channel shim (830, 344) can further comprisealignment tabs (383) on opposite corners. Sometimes, the channel shim(830, 344, 364) further comprises notches (381, 368, 369) on oppositeends.

The separator shim (840, 342, 362) can further comprise a mixingmanifold (345). The separator shim (840, 342, 362) can sometimes furthercomprise alignment tabs (385) on opposite corners. The separator shim(840, 342, 362) could alternatively further comprise notches (387, 420,422, 424) on opposite corners. The separator shim (840, 342, 362) mayfurther comprise indents (380, 426) on an end.

The heat exchanger, in some embodiments, further comprises a combustiongas source (111, 202, 611) at an end of the heat exchanger opposite theinlet manifold (812, 124, 120, 620, 640) of the first channel.

In some embodiments, the channel shim (540) comprises: an entry end(541) and a return end (542); two outer walls (543) and a central wall(544) that define two micro-channels (547, 548); and an alignment slot(545) in the central wall. In those embodiments, the separator shim(550) comprises: an entry end (551) and a return end (542); a centralslot (557) at the return end; two recesses (553) at the entry end thatalign with the micro-channels (547, 548) of the channel shim (540); andan alignment slot (555) that aligns with the alignment slot (545) of thechannel shim.

Also disclosed herein is a system (100, 200) for steam reforming,comprising: a reactor (110, 210) including a reformer (132, 136, 232,236) and a vaporizer (152, 154, 252, 254); a fuel supply (171, 271) forproviding fuel to the reactor; and a water supply (199, 299) forproviding water to the reactor. The vaporizer (152) operates to generatesteam from the water and the reformer (132) operates to generatehydrogen from a reformate mixture including the steam and the fuel.

The system may further comprise a start-up combustor (102) attached tothe reactor (110). The reactor (110, 210) can alternatively include aburner (111, 202) for combusting scrap reformate. In another embodiment,the start-up combustor (102) acts to combust scrap reformate. Thecombustion gas provided by the start-up combustor (102) or the burner(111, 202) may flow counter-current to the flow of the reformate withinthe reactor (110). The combustion gas provided by the start-up combustor(102) or the burner (111, 202) may flow counter-current to the flow ofthe water within the reactor (110).

The system may further include a fuel cell assembly (181, 281) connectedto the reactor (110, 210) for producing electricity. The fuel cellassembly (181) can include a proton exchange membrane fuel cell (PEMFC).In embodiments, the PEMFC is operative to generate from about 6 kW toabout 8 kW of electricity. However, the PEMFC can be applied to generatepower from about 1 kW to about 1 megawatt of electricity. Alternatively,the fuel cell assembly (281) includes a solid oxide fuel cell (SOFC).

The reformer (132, 136, 232, 236) or the vaporizer (152, 154, 252, 254)can include a stack assembly formed from a regular alternating patternof a separator shim and a channel shim.

Also disclosed herein is a method (S100) for forming a reactor,comprising: alternatingly stacking reformer channel shims (344) andreformer separator shims (342) to form a reformer shim stack (340);bonding the reformer shim stack (340) to reformer plates (332, 336) toform a reformer stack assembly (330); alternatingly stacking vaporizerchannel shims (362) and vaporizer separator shims (364) to form avaporizer shim stack (360); bonding the vaporizer shim stack (360) tovaporizer plates (352, 356) to form a vaporizer stack assembly (350);and arranging the reformer stack assembly (330) and vaporizer stackassembly (350) within a casing (119); wherein the reformer stackassembly includes a reaction channel and a combustion channel, whereinthe vaporizer stack assembly includes a vaporizer channel and acombustion channel, and the reformer stack assembly combustion channelcommunicates with the vaporizer stack assembly combustion channel todirect flow from the reformer stack assembly combustion channel into thevaporizer stack assembly combustion channel.

The arranging may further include arranging the inlets and outlets ofthe stack assemblies (340, 360) so that reactants and water flow in acounter-current direction to combustion gas. The method can furthercomprise placing a second reformer stack assembly in series with thereformer stack assembly (340); or further comprise placing a secondvaporizer stack assembly in series with the vaporizer stack assembly(360).

Any of the shims 342, 344, 362, 364 can be made by a wire electricaldischarge machining (EDM), water jet, laser cutting, or stampingproduction method. The bonding of the reformer shim stack 340 or thevaporizer shim stack 360 can be performed by diffusion bonding orbrazing. In some instances, automated welding may also be used.Sometimes, two channel shims (344) are stacked between each separatorshim (342).

Also disclosed in various embodiments herein is a fuel processing device(800, 110, 510, 610), comprising: a combustion gas source (111, 102,211, 202, 516, 611); a reaction channel (134, 135, 138, 139, 506, 632,636) having an inlet (124) and an outlet (128); a vaporizer channel(151, 652, 654) having an inlet (120) and an outlet (122); and acombustion channel (133, 153, 502, 504); wherein combustion gas from thecombustion gas source flows through the combustion channel. The reactionchannel inlet and the vaporizer channel inlet can be arranged so thatflow through the reaction channel and the vaporizer channel arecounter-current to the combustion gas flow.

The combustion gas source may be at least one of a burner (111, 211) andstart-up combustor (102, 202).

The device may further include at least one adiabatic reformer (117,118)connected to the reaction channel outlet.

The reaction channel may include a catalyst (131), such as rhodium onspinel. The catalyst (131) can be inserted into the reaction channel asa catalyst insert (734). The catalyst insert (734) may comprise acorrugated center piece (730) coated on at least one side with thecatalyst. The corrugated center piece (730) can be sandwiched betweentwo flat shims (736), wherein an inner surface (735) of each flat shimis also coated with the catalyst. Alternatively, the surfaces of thechannel (134) may be coated with catalyst.

In some embodiments, the combustion gas source is located at a burnerend (505) of the device, and wherein the combustion channel (502, 504)includes (i) a first leg (521) running from the burner end to anopposite end (501) of the device and (ii) a second leg (523) returningfrom the opposite end to the burner end.

Sometimes, the reaction channel (506) and the vaporizer channel eachinclude (i) a first leg (525) running from the burner end to an oppositeend of the device and (ii) a second leg (527) returning from theopposite end to the burner end.

In some embodiments, the reaction channel (632, 636) flowscounter-current to the first leg of the combustion channel and thevaporizer channel (652, 654) flows counter-current to the second leg ofthe combustion channel.

Also described herein is a heat exchanger assembly (800, 330, 350, 590)formed from a plurality of channel shims (344, 364, 540) and a pluralityof separator shims (342, 362, 550). The channel shims and separatorshims are stacked in a regular alternating pattern to form a shim stack(340, 360, 590). The channel shims and separator shims operate to form afirst channel (810), a second channel (820), and a fin (845, 341, 361,556) extending from the second channel into the first channel.

The assembly may further comprise a top plate (332, 352) above the shimstack and a bottom plate (336, 356) below the shim stack. The channelshims and the separator shims can be diffusion bonded together.

In embodiments, the first channel (810) has a plurality ofmicro-channels (811) and the second channel (820) has a plurality ofmicro-channels (821) The ratio of a first micro-channel width (836) to afirst micro-channel height (834) can be from 2:1 to 20:1. The ratio of achannel shim height (834) to a separator shim height (844) can be from0.125 to 8.

In some embodiments, the channel shim (344, 364) comprises a pluralityof micro-channels (346, 348, 365) extending from a first end of thechannel shim to a second end of the channel shim.

Each micro-channel (346, 348) can further comprise a mixing manifold(347).

Sometimes, two channel shims are placed between two separator shims andare used to form a single level between the separator shims.

The separator shim (342) can include a slot (386) at each end of theseparator shim, each slot aligning with an end of a micro-channel of thechannel shim. Sometimes, the separator shim (342) includes a mixingmanifold (345) that aligns with a micro-channel of the channel shim. Inaddition, the separator shim (342) can include a thermal slot (343) atthe center of the separator shim.

In some embodiments, each micro-channel (365) of the channel shim (364)is formed from two longitudinal walls (366) joined together by at leastone transverse support (367), the micro-channel thus being separatedinto a series of chambers, wherein the chamber at a first end of themicro-channel is shorter in length than the other chambers. The channelshim (364) may have only one notch (369) on an end.

In other embodiments, the channel shim (364) includes a plurality ofmicro-channels (365) spaced such that when one channel shim is stackedupon another channel shim, the micro-channels are aligned with eachother.

Sometimes, two channel shims (364) are placed between two separatorshims, and are used to form two levels between the separator shims, thechannel shims being rotated 180° with respect to each other. Theseparator shim (362) can include a slot (432, 434) at each end of theseparator shim, each slot aligning with an end of a micro-channel of thechannel shim.

In many different arrangements, the channel shim (344) further comprisesalignment tabs (383) on opposite corners; and/or notches (381, 368) onopposite ends. The separator shim (342, 362) can further comprisealignment tabs (385) on opposite corners; notches (387, 424) on oppositecorners; and/or indents (380, 426) on an end.

In particular embodiments of the assembly (590), the channel shim (540)comprises: an entry end (541) and a return end (542); two outer walls(543) and a central wall (544) that define two micro-channels (547,548); and an alignment slot (545) in the central wall. In otherparticular embodiments of the assembly (590), the separator shim (550)comprises: an entry end (551) and a return end (542); a central slot(557) at the return end; two recesses (553) at the entry end that alignwith the micro-channels (547, 548) of the channel shim (540); and analignment slot (555) that aligns with the alignment slot (545) of thechannel shim. One channel shim (540) may be used to form a single levelbetween separator shims.

A single shim stack can be from about 1 inch to about 20 inches inheight and from about 5 mm to about 15 mm in width. However, thedimensions of the shim stack can be varied in either direction to obtainthe desired output.

These and other non-limiting aspects and/or objects of the disclosureare more particularly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a diagram of a steam/hydrocarbon fuel reformation system thatincorporates a proton exchange membrane fuel cell (PEMFC).

FIG. 2 is a three-dimensional (3D) model of a first exemplary embodimentof a fuel processor of the present disclosure showing an externalperspective view. In this embodiment, the channels in the reformer andvaporizer are arranged linearly.

FIG. 3 is a plan view of the exterior of the fuel processor of FIG. 2(looking along the Y-axis).

FIG. 4 is an X-Y plane cross-sectional view of the fuel processor ofFIG. 2.

FIG. 5 is an X-Z plane cross-sectional view of the fuel processor ofFIG. 2 showing internal components within the casing.

FIG. 6 is a diagram of a steam/hydrocarbon fuel reformation system thatincorporates a solid oxide fuel cell (SOFC).

FIG. 7 is an external perspective view of a second exemplary embodimentof a fuel processor of the present disclosure. In this embodiment, thechannels in the reformer and vaporizer are arranged linearly.

FIG. 8 is an X-Z plane cross-sectional view of the fuel processor ofFIG. 7. Only a single layer of the reformer stack assembly and thevaporizer stack assembly are shown.

FIG. 9 is a diagram of an exemplary reformer stack assembly illustratedin an assembled view (left side) and an exploded view (right side).

FIG. 10 is a perspective view of top and bottom plates for the reformerstack assembly of FIG. 9.

FIG. 11 is a side cross-sectional view and magnified view of thereformer stack assembly of FIG. 9.

FIG. 12 is a diagram showing a shim stack for a reformer stack assembly,illustrated in an assembled view (left side) and an exploded view (rightside) showing the separator shim and the channel shim.

FIG. 13 is an exploded view showing an exemplary vaporizer stackassembly.

FIG. 14 is a perspective view of top and bottom vaporizer plates for thevaporizer stack assembly of FIG. 12.

FIG. 15 is a side cross-sectional view and magnified view of thevaporizer stack assembly of FIG. 13.

FIG. 16 is a diagram showing an alternating shim stack for a vaporizerstack assembly, illustrated in an assembled view (left side) and anexploded view (right side) showing the separator shim and the channelshims.

FIG. 17 is a flow diagram for methods for forming a fuel processor.

FIG. 18 is a conceptual diagram of a third exemplary embodiment of afuel processor of the present disclosure. In this embodiment, thechannels in the reformer and vaporizer are arranged to provide aU-shaped flow.

FIG. 19 is a diagram of an alternating reformer shim stack used in theembodiment of FIG. 18, illustrated in an assembled view (right side) andan exploded view (left side) showing the separator shim and the channelshim.

FIG. 20 is a model of a fourth exemplary embodiment of a fuel processorof the present disclosure, wherein the reformer and vaporizer sectionsare placed side-by-side.

FIG. 21 is a cross-sectional view of an exemplary embodiment of acatalyst insert which can be inserted into a channel of the reformer orthe vaporizer.

FIG. 22 is a conceptual diagram of a heat exchange assembly of thepresent disclosure.

FIG. 23 is a cross-sectional view of the heat exchange assembly takenalong line A-A of FIG. 22.

DETAILED DESCRIPTION

A more complete understanding of the processes and apparatuses disclosedherein can be obtained by reference to the accompanying drawings. Thesefigures are merely schematic representations based on convenience andthe ease of demonstrating the existing art and/or the presentdevelopment, and are, therefore, not intended to indicate relative sizeand dimensions of the assemblies or components thereof.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (forexample, it includes at least the degree of error associated with themeasurement of the particular quantity). When used with a specificvalue, it should also be considered as disclosing that value. Forexample, the term “about 2” also discloses the value “2” and the range“from about 2 to about 4” also discloses the range “from 2 to 4.”

It should be noted that many of the terms used herein are relativeterms. For example, the terms “interior” and “exterior”, or “central”and “end”, are relative to a center, and should not be construed asrequiring a particular orientation or location of the structure.Similarly, the terms “upper” and “lower”, “top” and “bottom”, or “above”and “below” are relative to each other in orientation, i.e. an uppercomponent is located at a higher elevation than a lower component in agiven orientation, though the orientation can be changed (e.g. byflipping the components 180 degrees). The terms “inlet” and “outlet” arerelative to a fluid flowing through them with respect to a givenstructure, e.g. a fluid flows through the inlet into the structure andflows through the outlet out of the structure. The terms “upstream” and“downstream” are relative to the direction in which a fluid flowsthrough various components, i.e. the flow fluids through an upstreamcomponent prior to flowing through the downstream component.

The terms “horizontal” and “vertical” are also used to indicatedirection relative to each other, and are not measured against anabsolute reference. The term “horizontal” refers to a plane defined by alongitudinal axis and a transverse axis, and the term “vertical” refersto a lateral axis extending out of the “horizontal” plane. However,these terms should not be construed to require structures to beabsolutely parallel or absolutely perpendicular to each other. Forexample, a first vertical structure and a second vertical structure arenot necessarily parallel to each other. The term “orthogonal” is used torefer to two axes that are perpendicular to each other.

The present disclosure relates broadly to a heat exchanger. The heatexchanger can be used in a reactor which can be applied to fuelreforming applications, or to any set of reactions where one reaction ishighly exothermic and another reaction is highly endothermic, or whereone reaction is either significantly endothermic or exothermic and heatneeds to be transferred to/from the reaction. The heat exchanger is alsoparticularly useful when the primary reaction is carried out at apressure significantly higher than the secondary reaction. The heatexchange can be operated using co-current flow (co-flow) orcounter-current flow (counter-flow).

The heat exchanger design is broadly illustrated in the plan view ofFIG. 22 and the cross-sectional view of FIG. 23 (taken along line A-A ofFIG. 22). The heat exchanger 800 includes two channels, a first channel810 and a second channel 820. Each channel has a height, length, andwidth. The first channel 810 and second channel 820 are separated by afirst wall 805. The two channels are defined by two shims havingdifferent shapes, a channel shim 830 and a separator shim 840. Thechannel shim provides a second wall 832 opposite the first wall. Theseparator shim provides a fin 845 that extends from the second channelinto the first channel, and passes through the first wall 805 andextends to the second wall 832, and acts as a heat transfer surface. Theheat transfer surface is present in both the first channel and thesecond channel.

The channel shim 830 and the separator shim 840 cooperate to form thefirst wall 805 that separates the first channel 810 from the secondchannel 820. The first channel includes a horizontal flowpath, as doesthe second channel. In addition, an inlet manifold 812 is present at oneend of the first channel, and an outlet manifold 814 is present at asecond opposite end of the first channel. These manifolds extendorthogonally to the horizontal flowpath (i.e. vertically), and permitaccess to the first channel.

As seen in the cross-sectional view of FIG. 23, each channel 810, 820includes a plurality of micro-channels 811, 821. The separator shim 840may be considered as providing a fin 845, and the interleaving fins 845and passages 811, 821 allow for high heat transfer from one channel tothe other channel. The micro-channels may be thought of as verticallayers that are combined to form the channel.

Generally, the channel shim defines the height of the micro-channels inthe two channels. The channel shim has a height 834. The channel shimalso has a width 836, which is measured between the two walls. Theseparator shim (i.e. fin) has a height 844. The ratio of the channelshim width 836 to the channel shim height 834 may be from 2:1 to 20:1.The ratio of the channel shim height 834 to the fin height 844 may befrom 0.125 to 8 (i.e. 0.125:1 to 8:1), or from 0.25 to 4 (i.e. 0.25:1 to4:1), or in more specific embodiments from 0.5 to 2. In this regard,thick fins (i.e. a ratio of 1 or lower) may be needed to enableeffective heat transfer for high temperature reactions, becausematerials that can withstand high temperatures typically have lowthermal conductivity values.

The interleaved fins 845 and passages 811, 821 allow a compact designthat can operate at high pressure because the fins provide support forthe walls 805, 832 of the channels. This is different than the usualconstruction for a heat exchanger, where fins are only attached to awall at one end (i.e. extend from a wall, with the other end hangingfreely). Here, extending the fins 845 across the entire channel (i.e.from first wall 805 to second wall 832) provides a strength benefit aswell as a heat exchange benefit. Additionally, adjusting the channelshim height 834 and the thickness of the walls 805, 832 enables adifferential pressure between 1 and 50,000 PSI to be accommodatedbetween the primary and secondary reaction occurring within the heatexchanger 800.

The present disclosure also relates to heat exchangers that can be usedas a fuel processor that accepts as inputs a hydrocarbon fuel and steam,and produces as outputs carbon monoxide and hydrogen gas. Generally, thefuel processor comprises a housing or casing in which a reformerassembly and a vaporizer assembly are located. Hot combustion gases flowfrom one end of the casing to the other end. The vaporizer assemblyconverts water to steam. The steam is combined with the hydrocarbon fueland then travels through the reformer assembly to be converted intocarbon monoxide and hydrogen gas. The water in the vaporizer assembly,and the fuel/steam mixture in the reformer assembly can flowcounter-current (180 degrees in the opposite direction) to the flow ofthe hot combustion gas. The reformer assembly and the vaporizer assemblyeach act as heat exchangers to facilitate the reactions needed for fuelprocessing. Alternatively, the water and the fuel/steam mixture can flowco-current to the hot combustion gas.

The reformer assembly and the vaporizer assembly are formed byalternating two different shim structures (i.e. a channel shim and aseparator shim) to form each assembly, and then joining the shimstogether. Previous shims have included fine-detailed geometry that limitfabrication options. Shim geometry is further complicated by in-channelcatalyst stand-offs, and chemical etching processes are the only way tomake some features of current shims. Many pieces must be assembledindividually into the combustion duct of current fuel processors, andthese pieces often occupy too large of a volume in order to achieve hotgas uniformity and between-panel spacing, making the reactor too large,Additionally, prior shims have long lengths of metal; when exposed toheat, such shims are heated to different temperatures along theirlength, which show a potential for thermal expansion stress of the shimand subsequent failure of the reactor. The present disclosure reducessuch problems.

FIG. 1 is a diagram of a steam/hydrocarbon fuel reformation system thatincorporates a proton exchange membrane fuel cell (PEMFC). The system100 includes a fuel processor assembly 101, a fuel supply 171, a fuelcell assembly 181, an air supply 191, and a water supply 199. The fuelprocessor assembly 101 includes a reactor 110 that operates as a fuelprocessor herein. This figure includes flow of four different fluids:air (marked A); water/steam (marked B); fuel or reformate (marked C);and combustion gas (marked D).

The system 100 begins with the fuel processor assembly 101 receivingfuel from fuel supply 171 and receiving air from air supply 191, whichare fed directly to the start-up combustor 102. The fuel supply 171 canbe JP8 low sulfur content fuel (approximately 125 ppm sulfur), morepreferably sulfur-free JP8, or generally any other combustiblehydrocarbon. Initially, the fuel processor assembly is at roughly roomtemperature. However, the steam/hydrocarbon reformation reactionrequires a temperature of about 300° C. when using fuels such asmethanol and between 300° C. and 850° C. when using fuels such asnatural gas before the overall system becomes self-sustaining. Thus, thestart-up combustor burns fuel to heat up the fuel processor 110 for thesubsequent steam-hydrocarbon fuel reformation reaction.

The start-up combustor 102 is also used to initially provide hotcombustion gas through the fuel processor 110. As the overallreformation reaction continues, air from the air supply 191 and scrapreformate from main separator 107 are supplied to a burner 111 in fuelprocessor 110. Scrap reformate gas includes mostly carbon monoxide gas,methane (CH₄) gas, and residual hydrogen gas. The burner 111 ignites thescrap reformate to provide hot combustion gas within the fuel processor110. Once the combustion reaction within burner 111 is self-sustainable,the start-up combustor 102 is no longer needed.

Continuing at the bottom left of FIG. 1, hot combustion gas travelingthrough the fuel processor 110 heats up the vaporizer sections 152, 154.These vaporizer sections receive water from water supply 199, which isheated to become hot steam. This hot steam can optionally be sent tosteam superheater 103 for additional heating before traveling to afuel-steam mixer 104. Alternatively, the steam from vaporizers 152, 154can travel directly to the fuel-steam mixer 104 without beingsuperheated. Steam may also be sent to the hydrodesulfurization (HDS)reactor 105 to pre-heat the HDS reactor 105 for HDS reactions to occurand to assist with the separation of hydrogen from reformate. Pleasenote that although only one arrow is drawn from vaporizer section 152 tosteam superheater 103, the steam from vaporizer section 154 can also besent to steam superheater 103. Similarly, the steam from vaporizersection 152 can also be sent to HDS reactor 105. It should be noted thatthe HDS reactor 105 is optional, and is not needed if the presence ofsulfur is acceptable.

At the fuel-steam mixer 104, steam is mixed with fuel from the fuelsupply 171 to form reformate. The reformate is sent to reformer sections132, 136 where the steam and fuel react with each other under hightemperature, in the presence of catalyst, to produce hydrogen gas (H₂)and carbon monoxide (CO) according to the classical steam reformationreaction in EON. 1:CH₄+H₂O(g)→3H₂(g)+CO(g)   (EQN. 1)

The output of the reformer sections 132, 136 may include the products ofthe reformation reaction (H₂(g) and CO(g)), as well as residual methane(CH₄(g)), carbon dioxide (CO₂(g)), and steam (H₂O(g)). The output ofreformer sections 132, 136 optionally can be sent through the steamsuperheater 103 to participate in a heat exchange reaction with thesteam that will be used to make new reformate. The output may thenoptionally go to a hydrodesulfurization (HDS) reactor 105. At the HDSreactor 105, a portion of the gaseous reformer output may be combinedwith raw fuel which contains sulfur. With the appropriate catalyst andprocessing conditions, the raw fuel is desulfurized for use later.Alternatively, a portion of the hydrogen may be extracted from thereformate to assist with the desulfurization reaction. For the PEMsystem of FIG. 1, the reformer output also passes through at least oneof a water-gas shift (WGS) reactor 106 or main separator 107. Theseparator in FIG. 1 separates hydrogen from the reformate which isdirected to the fuel cell assembly 181. The remaining components and anyhydrogen not removed from the reformate by the separator are directed tothe burner to provide the heat needed for the steam reforming reaction.The purpose of the shift reactor 106 is to increase the hydrogen contentof the reformate via a well known shift reaction:CO+H₂O→CO₂+H₂

At the main separator 107, hydrogen gas (H₂) is separated from thereformer output and routed to the fuel cell 181. The main separator 107routes the other components, including CO not converted by the WGSreactor, methane (CH₄) gas, and residual hydrogen gas not used by thefuel cell assembly 181, back to the burner 111 as scrap reformate fuelfor another steam/fuel reformation reaction cycle.

In FIG. 1, the fuel cell assembly 181 includes a proton exchangemembrane fuel cell (PEMFC) which allows the system 100 to produceapproximately a 6 kW to 8 kW net output of electricity. The amount ofelectricity produced by the system 100 may be increased with more PEMFCswhich can be fed with hydrogen gas input produced by the fuel processorassembly 101. As needed, additional reformer sections can be added tothe fuel processor 110. Alternatively, the reformer sections 132, 136can be increased in dimension to produce additional hydrogen gas.

The chemical reaction occurring at the fuel cell assembly 181 whenincluding a PEMFC is represented by EQN. 2:Anode:2H₂(g)→4H⁺+4e ⁻Cathode:O₂+4H⁺+4e ⁻→2H₂(l)+heat+oxygen depleted air   (EQN. 2)

Hydrogen gas provided from the main separator 107 enters a gas diffusionanode of the PEMFC assembly 181 where it is electrolyzed into protonsand electrons in the presence of metal catalyst, e.g., platinum. Protonsproduced at the anode travel across a proton exchange membrane to a gasdiffusion cathode, thereby “exchanging” protons from the anode to thecathode. Air from air supply 191 is provided to the cathode of the PEMFCassembly 181, which combines with protons to form water and heat.Electrons produced at the anode travel to the cathode through anelectron bridge, the flow of electrons creating an electrical current.In one embodiment, fuel processor 110 is used to produce approximately 6kW of net output electricity within system 100 when fuel cell assembly181 includes a PEMFC.

FIGS. 2-5 are different views of a first exemplary embodiment of a fuelprocessor. FIG. 2 is an external perspective view. FIG. 3 is an externalplan view of the top of the fuel processor. FIG. 4 is a sidecross-sectional view. FIG. 5 is a perspective cross-sectional view.

Referring now to FIG. 1 and FIG. 2 together, the fuel processor 110includes the burner 111 and optionally two adiabatic reformers 117, 118which are disposed upon the top of the casing 119. The burner 111 mayinclude one or more gas inlets 112 for receiving the scrap reformatefuel from the main separator 107. The burner 111 may further include oneor more igniters 113, thermocouple tubes 114, and air inlets 115 (whichsupply air from air supply 191). The start-up combustor 102 is shown asbeing integrally attached to the bottom of the casing, though thislocation can be changed as desired. The burner is located at one end ofthe casing. Combustion gas provided by either the startup combustor 102or combustion of scrap reformate fuel input by the burner 111 flowsthrough the casing 119 and exits at an exhaust port 129 located at theend of the casing opposite the burner. The casing 119 may be made fromany suitable casing material, including any suitable metal known to onehaving ordinary skill in the art.

Referring to FIG. 3, vaporizer inlets 120 are shown here as beinglocated at the end of the casing 119 adjacent the exhaust port 129.Vaporizer outlets 122 are located closer to the center of the casing119. Reformer inlets 124 are also located near the center of the casing.As shown here, there are a total of four reformer inlets, with two ofthem being considered inner reformer inlets 125. Reformer outlets 128are located at the end of the casing 119 adjacent the burner 111. Asshown here, there are a total of four reformer outlets, with two of thembeing considered inner reformer outlets 127. Sample outlets 126 are alsoprovided between the reformer inlets 125 and the reformer outlets 128.The two adiabatic reformers 117, 118 are also visible.

Referring now to FIG. 1 and FIG. 3 together, water from the water supply199 enters the vaporizer 152/154 at vaporizer inlets 120. The water isheated by hot combustion gases within fuel processor 110, and exits thevaporizer outlets 122 as steam. This steam can be sent to steamsuperheater 103, fuel-steam mixer 104, or HDS reactor 105 as previouslydescribed. The reformate produced at the fuel-steam mixer 104 enters thereformer 132, 136 through reformer inlets 124. The reformate will travelthrough one of the reformer sections from an inlet 124 to the reformeroutlet 128 while being heated by surrounding combustion gases withinfuel processor 110. A majority of the reformate is converted to productsH₂ (g) and CO (g) according to EQN. 1 by the time the reformate reachesreformer outlets 128. Experimental samples may be taken through sampleoutlets 126 to access the progress of the reformation reaction. Theoutput from reformer outlet 128 may then be directed to an adiabaticreformer 117, 118 which provides additional reaction time at hightemperature to continue the reforming reaction. The use of adiabaticreactor(s) as shown is considered as an optional cost reduction measureapplicable to some configurations. The reformate and/or reformationproducts subsequently travels back to another reformer inlet (here,inner reformer inlet 125) and then travels again through the interior ofthe casing 119 for another reformation reaction cycle. In the secondcycle, the reformate exits from inner reformate outlets 127. Thereformation products then travel to either the optional steamsuperheater 103 or the HDS reactor 105.

Referring now to FIG. 4, the fuel processor 110 includes the burner 111at one end and the exhaust port 129 at the opposite end of the casing.Located adjacent the burner is the reformer stack assembly 130. Asexplained further herein, the reformer stack assembly is comprised ofstacked metal shims which are bonded together by, for example, diffusionbonding. The reformer outlets 128, sample outlets 126, and reformerinlets 124 travel down the vertical height (y-axis) of the reformerstack assembly 130. The fuel processor 110 also includes a vaporizerstack assembly 150 which, similar to the reformer stack assembly 130, iscomprised of stacked metal shims which are diffusion bonded together.Vaporizer outlets 122 and vaporizer inlets 120 travel down the verticalheight (y-axis) of the vaporizer stack assembly 150.

The perspective view of FIG. 5 through fuel processor 110 shows thereactor sections 132, 136 and vaporizer sections 152, 154 withinreformer stack assembly 130 and vaporizer stack assembly 150,respectively (see FIG. 1).

Referring now to FIG. 1, FIG. 3, and FIG. 5 together, counter-currentflow (i.e. counter-flow) of the reactant gases and combustion gaseswithin fuel processor 110 can be visualized. The reformer stack assembly130 of FIG. 5 includes the reformer sections 132, 136 of FIG. 1.Reformer section 132 (FIG. 1) includes a reformer combustion channel 133surrounded on two sides by an outer reaction channel 134 and an innerreaction channel 135 (FIG. 5) along the width of the processor.Similarly, reformer section 136 includes a reformer combustion channel137 surrounded on two sides horizontal passageway by an outer reactionchannel 138 and an inner reaction channel 139.

Referring to FIG. 5, the reaction channels 134, 135, 138, 139 areaccessed by orthogonal passageways at either end of the channels. Putanother way, fluid flows through each reaction channel through thevertical passageways and a horizontal flowpath between the two verticalpassageways, in a U-shape. Fluid will flow through each combustionchannel 133, 137 in a straight line from one end to the other, i.e.through only a horizontal passageway. Again, these orientations arerelative, not absolute. The reaction channel and the combustion channelcan also be described as having parallel flowpaths, with the reactionchannel also including orthogonal passageways for accessing theflowpath.

In use, reformate will enter the outer reaction channel 134 of reformersection 132 at reformer inlet 124 and, in a first cycle, travel toreformer outlet 128. As seen in FIG. 3, the reformate from outlet 128will then travel through adiabatic reformer 117 and then enter reformersection 136 through inner reformer inlet 125. In a second cycle, thereformate then travels through inner reaction channel 139 towards innerreformer outlet 127. Concurrently, hot combustion gas originates fromeither start-up combustor 102 or burner 111 and travels through reformercombustion channels 133, 137 towards exhaust port 129. The combustiongas travels in the direction from burner 111 to exhaust port 129. Thereactant gases travel in the direction from exhaust port 129 towardsburner 111, i.e. 180 degrees different from the combustion gas. The twoflow paths are parallel to each other, but in opposite directions, i.e.counter-current flow. Of course, the fuel processor could be operated inco-current flow by reversing the locations of the burner 111 and theexhaust port 129, and maintaining the direction of flow in the reactionchannels.

FIG. 5 reveals additional details of the burner 111. Burners 116 arelocated adjacent reformer sections 132, 136. Burners 116 combust scrapreformate coming from gas inlets 112, and the hot combustion gas flowsthrough the combustion reactor channels 133, 137 and through fuelprocessor 110 towards exhaust port 129. Other burners known to onehaving ordinary skill in the art may be used in this position if theyprovide appropriate flame geometry.

The concept of counter-current flow also applies to the vaporizer. Thevaporizer stack assembly 150 of FIG. 5 includes the vaporizer sections152, 154 of FIG. 1. The vaporizer stack assembly includes an alternatingseries of vaporizer water channels 151 and vaporizer combustion channels153 across its width. The channels 151, 153 of the vaporizer stackassembly are along the same axis as the channels 133, 134, 135, 137,138, 139 of the reformer stack assembly, or put another way the channelsare parallel. Water enters the vaporizer water channel 151 throughvaporizer inlet 120 and travels to vaporizer outlet 122. Combustion gastraveling through vaporizer combustion channels 153 will transform thewater to water/steam mixture or steam.

Reaction channels 134, 135, 138, 139 differ from vaporizer waterchannels 151 in the presence of catalyst 131. The catalyst 131 catalyzesthe highly endothermic reformation reaction in EQN. 1. The catalyst 131is preferably a highly active precious metal catalyst known to onehaving ordinary skill in the art. For example, the catalyst may be aspinel catalyst. The catalyst 131 may be coated on a corrugated materialwhich is inserted into reaction channels 134, 135, 138, 139. Thecatalyst 131 can also be coated on a flat rectangular material that isinserted into the reaction channels 134, 135, 138, 139 on either side ofthe catalyst-coated corrugated material to provide a flow passagecompletely surrounded by catalyst. Alternatively, the catalyst 131 isdirectly coated onto walls of reaction channels 134, 135, 138, 138 toprovide equivalent configuration in combination with the catalyst-coatedcorrugated material. Catalyst-coated corrugated materials may bepreferable due to open flow passages yielding low pressure drop and goodcatalyst contacts. Alternate catalyst support materials such as metalfoam or a metal screen may be beneficial. The metal screen may becorrugated, or the metal foam may be a simple insert.

The reaction channels 134, 135, 138, 139 also differ from vaporizerwater channels 151 in the presence of a mixing manifold 140 within eachchannel 134, 135, 138, 139 (shown here at the center of the channel).The mixing manifold 140 provides some mixing between the variousmicro-channels/levels/layers within each channel. The mixing manifoldalso provides an entry point for samples to be extracted through sampleoutlets 126 (see FIG. 3) to assess reformation reaction progress ifdesired. Additionally, the catalyst 131 may be placed into the mixingmanifold along a retainer. Some vertical mixing may also occur. However,it should be noted that the presence of the mixing manifold 140 is notnecessary.

FIG. 6 is a diagram of a steam/hydrocarbon fuel reformation system thatincorporates a solid oxide fuel cell (SOFC). The fuel processor assembly201 includes a reactor 210 that operates as a fuel processor herein.This figure includes flow of five different fluids: air (marked A);water/steam (marked B); fuel or reformate (marked C); combustion gas(marked D); and hydrogen (marked E).

The system 200 includes a fuel processor assembly 201, a fuel supply271, a fuel cell assembly 281, an air supply 291, and a water supply299. The system 200 begins with the clean fuel burner 202 receivingfuel, which may be from a separate burner, or the fuel supply 271 (notshown). Hot combustion gas travels from clean fuel burner 202 to fuelprocessor 210, where the combustion gas flows through the fuel processor210. Water from water supply 299 enters vaporizer sections 252, 254 andis heated to steam by the hot combustion gas flowing counter-current tothe water flow. The steam optionally travels to a steam superheater 203for further heating before traveling to a fuel-steam mixer 204.

At fuel-steam mixer 204, the steam is mixed with fuel supplied by fuelsupply 271. The steam/fuel mixture enters reformer sections 232, 236.The steam/fuel mixture reacts under high temperature in the presence ofa catalyst (not shown) to produce hydrogen gas (H₂) and carbon monoxide(CO) according to the classical steam reformation reaction in EON. 1.

The output of the reformer sections 232, 236 includes the products ofthe reformation reaction (H₂(g) and CO(g)), as well as residual methane(CH₄(g)), carbon dioxide (CO₂(g)), and steam (H₂O(g)). The output ofreformer sections 232, 236 optionally travels to the reformaterecuperator 209 and then to the HDS assembly 205 where the reformate iscooled and some hydrogen is extracted while at pressure. The reformatethen flows back to the reformate recuperator 209 and is reheated. Thereheated, now low pressure reformate can then pass through the adiabaticreformer 208 to react more of the methane into hydrogen and CO (greatermethane reforming is possible at lower pressure) before entering thefuel cell assembly 281.

The fuel cell assembly 281 includes a solid oxide fuel cell (SOFC) whichallows system 200 to produce approximately 2 kW to 4 kW net output ofelectricity, though the system can be scaled to produce between 1 kW andseveral megawatts of electricity. The amount of electricity produced bysystem 200 may be increased with more SOFCs which can be fed with ahydrogen gas or reformate input. Again, more hydrogen can be produced byadding more reformer sections or by increasing the dimensions of theexisting reformer sections.

The chemical reaction occurring at the fuel cell assembly 281 whenincluding a SOFC is represented by EON. 3:Anode:2H₂(g)+2O²⁻→2H₂O+4e ⁻Cathode:O₂(g)+4e ⁻→2O²⁻  (EQN. 3)

Air from air supply 291 is provided to a cathode of the SOFC assembly281, where it breaks up to produce oxygen ions. The oxygen ions passthrough a solid ceramic electrolyte to get to an anode. Hydrogen gas orreformate provided from the adiabatic reformer 208 then enters the anodeof the SOFC assembly 281 and breaks apart into ions. Hydrogen ions atthe anode combine with oxygen ions traveling from the cathode to producewater. The water and any excess fuel leave the anode and are sent to theclean fuel burner 202 for combustion (in the presence of air from airsupply 291), restarting the fuel cycle. Splitting apart the hydrogenatoms at the anode produces electrons and electrical current. Theelectrons are routed back to the cathode through a bridge and areconsumed when oxygen is split into ions at the cathode. In embodiments,fuel processor 210 can produce 2 kW of net output electricity withinsystem 200 when fuel cell assembly 218 includes a SOFC.

FIG. 7 and FIG. 8 are different views of a second exemplary embodimentof a fuel processor. FIG. 7 is an external perspective view. FIG. 8 isan internal view through the X-Z plane.

Referring to FIG. 7, the fuel processor 210 can be attached to a fuelburner 202 that provides hot combustion gas, without a separate burneror start-up combustor (see reference numerals 111, 102 in FIG. 2). Fuelprocessor 210 includes a casing 219 upon which are disposed reformeroutlets 228, sample outlets 226, reformer inlets 224, vaporizer outlets222, and vaporizer inlets 220. The casing 219 further includes anexhaust port 229 opposite the fuel burner 202. As seen by the number ofinlets and outlets, this casing would hold two reformer sections andthree vaporizer sections.

Referring to FIG. 8, the interior of fuel processor 210 is visible andshows locations for a reformer stack assembly 230 and a vaporizer stackassembly 250. These sections are smaller in this embodiment compared tothat seen in FIG. 5. Tabs 255 are present for use when placing thereformer stack assembly 230 into the casing 219, to fix the assembly inplace. The casing 219 here is shown as being made in two pieces, and abolt/washer/nut assembly 257 is used to secure the two pieces together.In other embodiments, the casing 219 is made from four pieces. Othersecuring arrangements can also be used.

FIG. 9 shows a heat exchanger/reformer stack assembly 330 illustrated inan assembled view (left side) and an exploded view (right side). Thereformer stack assembly 330 provides the reformate reaction channels andreformate combustion channels. The reformer stack assembly 330 may befabricated by diffusion bonding an alternating stack of shims 340 ofappropriate design. Each shim 342, 344 may be manufactured by wireelectrical discharge machining (EDM) in stacks of 10 to 200 at one time.Other shim manufacturing methods include water jet, laser cutting, orstamping/punching production methods.

The reformer stack assembly 330 may be assembled with the aid ofalignment pins 335 used to align plates 332, 336 and shims 342, 344. Thepins 335 can be removed after assembly. Care should be taken to minimizeshifting of the alternating shim stack 340 during the bonding process.

As seen on the right side, the reformer stack assembly 330 is assembledby first inserting the bottom plate 336 upon the alignment pins 335. Twotypes of shims are used, a channel shim 344 and a separator/fin shim342. These shims are used to form levels, with the shim in each levelbeing alternated. As illustrated here, one channel shim 344 is placedabove bottom plate 336 to form one level. Next, one separator shim 342is placed above the channel shims to form the next level. The shims arealternated to form the shim stack 340. The top plate 332 is finallyplaced. The alternating stack 340 can be formed by an appropriatenumbers of separator shim/fins 342, e.g. 25-54 separator shim/fins 342,and 52-110 channel shims 344 stacked between each other. The alignmentpins 335 are shown here as being removed from the stack 340. Thisalternating pattern of shims creates the reaction channels andcombustion channels seen in FIG. 5 in the reformer stack assembly, witheach channel being formed of vertical layers/micro-channels throughwhich fluid can pass. This structure can also be seen in FIG. 23.

FIG. 10 is a perspective view of the top plate 332 and the bottom plate336. Plates 332, 336 may be manufactured from 0.125 mm thick rolledannealed (RA) Inconel 625 high performance alloy or other oxidationresistant material as appropriate for the temperature of the reactionbeing supported. For example, if the reforming reaction is beingperformed on methanol, the reaction temperature of approximately 300° C.may allow the use of common stainless steel such as 316. Other reactionsmay require other materials such as 309 or 310 stainless steel or othervarious materials as are well known to one having ordinary skill in theart.

The top plate 332 and the bottom plate 336 are similar in many respectsto each other and to the separator shim 342. The central portion of eachplate, where the channels will be located, includes a surface. Eachplate includes two alignment tabs 333 on opposite sides which can bevisually inspected during bonding to ensure that all shims 342, 344 inalternating shim stack 340 are aligned properly. Each plate includesfour notches 331 on opposite ends through which the alignment pins 335are inserted. Each plate also includes two indents 370 (here having atriangular shape) on opposite ends as a visual indication of where thecombustion channel will be located. Several slits 372 are made in theplate along the linear axis corresponding to the combustion channel.These slits allow for differential thermal expansion between the hotterfin material and the cooler reactor channel. The slits also limitlongitudinal conduction in the fin and improve heat transferperformance.

T-slot 374 is designed to interact with the tab 255 of the casing. Afterthe stack of shims are bonded together, the ends of the stack aremachined away to reveal an open manifold on either end. With themanifold open, catalyst supports can be inserted in the reactionmicro-channels. The manifold can then be closed up by sliding in the tab255 and sealed by welding it closed.

The top plate 332 also includes features that are not present on thebottom plate 336. More particularly, the top plate includes holes 337,338, and 339 that allow access to the channels in the reformer section.Holes 337, 338, and 339 correspond to reformer outlets 128, sampleoutlets 126, and reformer inlets 124 of FIG. 4, respectively.

Referring now to FIG. 11, the reformer stack assembly 330 in onespecific embodiment may be approximately 15.222 mm in width and between2.54 and 5.15 mm in height. Due to the design of the reformer stackassembly 330, the micro-channels may be may be made wider than in priorart devices for similar temperature and pressure operating conditionswhile maintaining lower material stresses.

FIG. 12 shows a partially exploded view of the shim stack 340 of FIG. 9.To properly interface with the top plate 332 and bottom plate 336, thebottom layer and the top layer of the shim stack 340 must be channelshims 344. As illustrated here, two channel shims 344 are used betweeneach separator shim/fin 342. This allows the combustion gases to flowthrough the micro-channels formed by the channel shims.

Each channel shim 344 defines a first reaction micro-channel 346 and asecond reaction micro-channel 348 with characteristic dimensions on theorder of 0.5 to 2 mm in height and a width of 5 mm to 25 mm. A mixingmanifold 347 is indicated in each micro-channel (as a square), and formsan orthogonal passageway/channel through which a sample volume can beobtained from the reaction channel (i.e. this is the channel to whichsample outlet 126 of FIG. 1 connects). The channel shim also includesalignment tabs 383 on opposite corners, and notches 381 on opposite endsof the shim through which the alignment pins 335 are inserted.

Separator shim 342 serves to laterally conduct heat from a combustiongas pathway into reaction micro-channels 346, 348 through fin 341 whichextends into and across the reaction channels when shims 342, 344 arestacked into the final alternating shim assembly 340. The separator shimis very similar in structure to the top plate 332 of FIG. 10. Theseparator shim includes a fin that provides a heat transfer surface. Twoalignment tabs 385 are present along opposite sides of the separatorshim which can be visually inspected during bonding to ensure that allshims are aligned properly. The separator shim includes four notches 387in the corners through which the alignment pins 335 may be inserted. Theseparator shim also includes indent 380 (again shown as a triangularshape) on opposite ends as a visual indication of where the combustionchannel will be located. Several slits 384 are made in the separatorshim along the linear axis corresponding to the combustion channel.These slits allow for differential thermal expansion between the hotterfin material and the cooler reactor channel temperature. The slits alsolimit longitudinal conduction in the fin and improve heat transferperformance.

The separator shim 342 includes eight slots 386, four each on oppositeends along the linear axis. These slots align with the micro-channels346, 348 of the channel shim 344. Referring to FIG. 4, these slotscorrespond to the locations for the reformer outlets 128 and thereformer inlets 124, and subsequently form vertical passageways at bothends of the reaction channel. A mixing manifold slot 345 is alsoincluded along the center of the shim, which is slightly more elongatedalong the linear axis than the mixing manifold 347 of channel shim 344.This extra length permits sample mixing as reformate passes betweenstacked shims 342, 344. A thermal slot 343 is also present along thecenter of the shim, extending slightly in the transverse axis. Thisthermal slot 343 permits mixing of combustion gases as they flow throughthe micro-channels 334 within reformer stack assembly 330. The thermalslot 343 may also be used to reduce heat transfer to the mixing manifold347 where carbon formation may occur. The combination of reactionmicro-channels forms the reaction channel, and the combination ofcombustion micro-channels forms the combustion channel. The slots 386and indent 380 could be described as forming a transverse line at eachend of the separator shim. The mixing manifolds 345 and thermal slot 343could be described as forming a transverse line at a central portion ofthe separator shim.

FIG. 13 shows an exploded view of a heat exchanger/vaporizer stackassembly 350. The vaporizer stack assembly 350 may be made in a similarmanner as the reformer stack assembly 330 described in FIGS. 9-12. Topplate 352 is placed upon alternating shim stack 360, where thealternating shim stack includes 58 separator shims 362 and 118 channelshims 364 (as depicted here). Alignment pins 355 are used to guide thestacking of shims 362, 364 between plates 352, 356. As will be discussedfurther herein, here, two levels are made of channel shims 364, then onelayer is made of separator shim 362, and the levels alternate in thismanner.

FIG. 14 is a perspective view of the vaporizer top plate 352 and bottomplate 356. Plates 352, 356 may be manufactured from 11 gauge (0.120 mm)thick, 316/316L cold rolled & annealed stainless steel sheet. Scratches,deposits, and oxidation on the surface of plates 352, 356 should beavoided.

The top plate 352 and the bottom plate 356 are similar in many respects.Each plate includes two alignment notches 400, 402 which can be visuallyinspected during bonding to ensure that all shims 362, 364 inalternating shim stack 360 are aligned properly. The alignment notches400, 402 are offset from each other, or in other words are on oppositeends and opposite sides of the shim. Each plate also includes fournotches 404 on opposite ends through which the alignment pins 355 areinserted. Each plate also includes indents 406 (here having arectangular shape) on one end as a visual indication of where thecombustion channel will be located.

Several slits 408 are made in the plate along the linear axiscorresponding to the combustion channel. The slits 408 may allow fordifferential thermal expansion between the hotter fin and the coolerreactor channel. The slits 408 also limit longitudinal conduction in thefin and improve heat transfer performance. In addition, alignmentrecesses 410 are present in the corners of the plates, which caninteract with tabs on the interior of the casing to fix the stacks inplace. The ends of the stack assembly will then be machined away toexpose the micro-channels.

The top plate 332 also includes features that are not present on thebottom plate 336. More particularly, the top plate includes holes 412,414 that correspond to vaporizer inlets 120 and vaporizer outlets 122 ofFIG. 4, respectively.

With reference to FIG. 15, the bonded vaporizer stack assembly 350 inone embodiment may be approximately 5.11 mm in width and approximately5.15 mm in height. Due to the design of the vaporizer stack assembly350, the micro-channels may be may be made wider than in prior artdevices for similar temperature and pressure operating conditions whilemaintaining lower material stresses.

FIG. 16 is an exploded view of the alternating shim stack 360 of FIG.13. In one embodiment, 118 channel shims 364 and 58 separator shims 354are alternatingly stacked upon each other in a 2:1 ratio. The separatorshim/fin 354 can be manufactured from 18 gauge (0.48 mm) thick 316/316Lcold rolled and annealed stainless steel sheet or other materialsappropriate to the operating temperature. The channel shim 364 can bemanufactured from 26 gauge (0.018 mm) thick 316/316L cold rolled andannealed stainless steel sheet or other material appropriate to theoperating temperature. The alternating shim stack 360 must begin and endwith channel shims 364 to properly interface with top 352 and bottom 356plates.

Each channel shim 364 is shaped to create a series of combustionmicro-channels 363 and vaporizer micro-channels 365 extending betweenopposite ends of the shim. Combustion gas passes through the combustionmicro-channels, while water flows through the vaporizer micro-channelsand is converted to steam. Each vaporizer micro-channel 365 is formed bytwo longitudinal walls 366 which are joined together by at least onetransverse support 367. This causes the vaporizer micro-channel to beseparated into a series of chambers. All of the end chambers 358 at onea first end of the channel shim 364 are shorter in length than the otherchambers 359. This is because the longitudinal walls 366 and thetransverse support 367 are the same height. As a result, when twochannel shims are stacked upon each other, but are rotated 180 degreesin the same plane with respect to each other, the end chambers 358 areon opposite ends of the vaporizer channel 365. This permits water toflow up and down over the transverse supports, which would otherwise actas barriers to fluid flow, and travel in a tortuous path all the waythrough the micro-channel. Put another way, the channel shims must berotated about the lateral axis or flipped along the transverse axis, notflipped along the longitudinal axis.

Thus, the channel shim includes only one notch 369 on one end of theshim. This provides another visual indicator to confirm that the channelshims are properly stacked upon each other. Thus, the alternating stack360 includes two levels of channel shims 364, then one level ofseparator shim 362, then two levels of channel shims 364, etc. Eachchannel shim 364 also includes four notches 368 in the corners throughwhich the alignment pins 355 may be inserted. The combination ofvaporizer micro-channels forms the vaporizer water channel, and thecombination of combustion micro-channels forms the combustion channel.

Separator shim 362 serves to laterally conduct heat from a combustiongas pathway into vaporizer water channels through fin 361 which extendsinto and across the water channels when shims 362, 364 are stacked intothe final alternating shim assembly 360. The separator shim 362 is verysimilar to the top plate 352 in many respects except thickness. The shimincludes two alignment notches 420, 422 which can be visually inspectedduring bonding to ensure that all shims 362, 364 in alternating shimstack 360 are aligned properly. The alignment notches 420, 422 areoffset from each other, or in other words are on opposite ends andopposite sides (i.e. opposing corners) of the shim. Each plate alsoincludes four notches 424 in the corners through which the alignmentpins 355 are inserted. Each plate also includes indents 426 (here havinga rectangular shape) on one end as a visual indication of where thecombustion channels will be located. Several slits 428 are made in theplate along the linear axis corresponding to the combustion channels topermit differential thermal expansion. Slots 432, 434 are provided thatcorrespond to vaporizer inlets 120 and vaporizer outlets 122 of FIG. 4,respectively.

Again, the assembly forms two types of channels, water channels andcombustion channels. The water channels (formed from the micro-channels365) will have a horizontal flowpath and two orthogonal (i.e. vertical)passageways, while the combustion channels (formed from themicro-channels 363) will have only a horizontal flowpath and does nothave vertical passageways.

The processing capacity of the heat exchangers and fuel processorsdescribed herein can be scaled as desired to any convenient size in atleast two different ways. First, the alternating channel shims andseparator shims can be stacked vertically to any desired height toprovide the requisite number of channels and change the size of thereformer/vaporizer. Alternatively, the total number of channels definedby the channel shims and separator shims can be increased to provide thedesired capacity. For example, the embodiment of FIG. 12 has fourreaction channels, and the embodiment of FIG. 16 has six reactionchannels. In other words, the device can be made either taller or wider.

FIG. 17 is a chart illustrating a general method for forming a reactor,which starts at S101. First, the stack assemblies that make up thereformer and the vaporizer are made. At S102, the channel shims 344, 364and separator shims 342, 362 for the respective assembly are generated.At S104, the channel shims 344, 364 and separator shims 342, 362 arestacked alternatingly between the top plate 332, 352 and the bottomplate 336, 356. In optional step S106, catalyst inserts may be insertedinto the desired channels (see discussion of FIG. 21 below). Next, atS108, the shims and plates are bonded together to form the stackassembly 330, 350. Bonding may occur through diffusion bonding, with orwithout the help of alignment pins 335. At S110, post-processing of thestack assembly occurs. This may entail removing excess material, openingmanifolds, and attaching appropriate flow connections.

Next, the reactor can be formed. At S112, the reformer assembly and thevaporizer assembly are made, as described above. At S114, the inlets andoutlets of the reformer and vaporizer assemblies 340, 360 are arrangedso that reactants/water flow counter-current or co-current past thecombustion channels in the two assemblies. The arrangement may involvebinding the assemblies to the manifold or casing 119, 219 of a fuelprocessor assembly 110, 210, inserting the inlet/outlet tubes, andconnecting the reactant/water supply sources to the appropriate end ofthe assemblies. At S116, if desired, additional reformer assemblies 340can be arranged in series with the reformer assembly 340 to increase theoutput of hydrogen gas produced by the fuel processor. This may beperformed to meet greater fuel input demands by a fuel cell assembly181, 281 capable of generating more electricity. Additional vaporizerassemblies 360 may also be added in series with the reformer assemblies340 to provide more hot steam input to reformer assemblies 340.

FIG. 18 is a plan view of a third exemplary embodiment of a fuelprocessor 510 having counter-current flow between the combustion gas andthe reactants/water. This embodiment differs from the prior embodimentsin that the flow path is U-shaped, rather than linear. Put another way,the burner and the exhaust port are on the same end of the casinginstead of on opposite ends. This embodiment shows only the half of thefuel processor that contains the reformer section; the other half is ofa similar construction but contains the vaporizer section. FIG. 19 showsa channel shim and a separator shim used in this embodiment, which maybe helpful in visualizing the flow paths.

A burner 516 provides hot combustion gas which flows (indicated asdotted arrow) through two combustion channels 502, 504. The combustionchannels are optionally separated by a separator panel 508, which may bea ceramic panel used to direct hot combustion gas flow through thecombustion channels. The ceramic panel may also radiate thermal energyto increase net heat transfer in the combustion channel. As shown here,each combustion channel 502, 504 starts near the center of the processorand travels down a first leg 521 from the burner to the opposite end 501of the casing. The combustion channel then makes a U-turn and returnsdown a second leg 523 to the burner end 505 of the casing 503 near theoutside of the processor.

A reaction channel 506 is surrounded by the combustion channel 502. Thereaction channel also has a first leg 525 and a second leg 527. Asillustrated here (solid arrows), the steam/fuel mixture enters thereaction channel at the burner end near the outside of the processor andflows counter-current to the combustion gas down the first leg. At theopposite end 501, the reaction channel makes a U-turn and returns to theburner end 505 near the center of the processor in the second leg. Acentral slot 511 is present here. Catalyst 519 is present within thereaction channel, as described above with respect to FIG. 5.

At the center of the reaction channel 506 is a separating wall 510. TheU-turn for the reaction channel goes around this separating wall. Asseen later, the separating wall serves to align the shims of thisprocessor.

As noted above, FIG. 18 shows only the section of the processor thatperforms reformation. The section of the processor that contains thevaporizer and produces the steam has essentially the same construction.The only difference is that instead of a steam/fuel mixture entering thereaction channel 506, water enters the vaporizer channel of thevaporizer. The steam is then produced by heat transfer from thecombustion channel of the vaporizer. The vaporizer and reformer sectionscan share the same burner, which provides the combustion gas to bothsections. The two sections would be separated from each other by a wall.Alternatively, hot combustion gas leaving the reformer can be directedto a vaporizer so that the vaporizer is essentially in series with thecombustion gases of the reformer.

Referring now to FIG. 19, a perspective view of the channel shim 540(top left) and the separator shim 550 (bottom left) are provided, alongwith a partial assembly view (right side) of the heat exchanger assembly590 formed therefrom.

The channel shim 540 has an entry end 541 and a return end 542. Thereare two outer walls 543 and a central wall 544 having an alignment slot545. These walls create two micro-channels 547, 548. Two wings 546 arepresent extending from the outer walls 543 on the entry end 541. A notch549 is present on the outer edge of the return end aligned with thecentral wall 544.

The separator shim 550 has an entry end 551 and a return end 552. Theentry end includes two recesses 553 that align with the micro-channelsin the channel shim. An alignment slot 555 is present in the center, andaligns with the alignment slot 545 of the channel shim. The return endcan be described as having fins 556. A central slot 557 is located atthe return end, and aligns with the micro-channels in the channel shim.A notch 559 is present on the center of the outer edge of the returnend.

As seen on the right side of FIG. 19, the channel shim 540 and separatorshim 550 are alternated. Their alignment slots 545, 555 align so thatthe separating wall 510 passes through the slots. The reformate willfirst pass through the micro-channel 547. At the return end 542, 552,the reformate can pass through the central slot 557 to move frommicro-channel 547 to micro-channel 548 and flow back towards the entryend. The reformate inlet 560 and reformate outlet 562 are marked. Thecombustion channel is on the exterior, surrounding the reformate channel547/548.

In this regard, because the combustion channel contains relativelyhotter combustion gas on the beginning leg compared to the return leg,the reformer can be divided into a hot side and a cold side (hot andcold being relative terms). Referring back to FIG. 19, the hot side 570is proximate the center of the processor, while the cold side 572 isnear the outside of the processor. It should be noted that the separatorshim 550 will transfer heat laterally from the hot side to the cold sideas the combustion gas travels from the burner to the opposite end 501 ofthe casing. The resulting heat gradients in the reaction channel 506 aredesigned so that relatively hotter reformate passes through the hot side570, so that overall the reformate is more gently heated. This shouldreduce excessive carbon deposits on catalyst 519.

In one embodiment of fuel processor 510, the channel shims 540 arefabricated from 0.040 inch thick sheet while the separator/fin shims 550are made from 0.050 inch thick sheet, allowing the combustion channels502, 504 to see a stack of fins spaced 0.040 inch apart which providessignificant extended heat transfer surface area. The thickerseparator/fin shims 550 allow for effective heat transfer using hightemperature materials, e.g. Inconel and the like, that have low thermalconductivity.

In another embodiment of fuel processor 510, the catalyst 519 issupplied on shims that are approximately 3½ inches long and ⅜ inch wide.In yet another embodiment, the catalyst 519 adopts an alternativeconfiguration with longer, narrower shims. A larger catalyst 519 insertwidth is convenient for insertion into long reaction channels. Becausethe pressure above and below the separator shim 550 is the same, thereis no strength issue with additional catalyst 519 as long as heat fromhot combustion gas can be transferred effectively to the catalysts 519.In yet another embodiment of fuel processor 510, the catalyst 519inserts are expanded metal that have been corrugated parallel to thereaction channels to provide consistent flow space. The catalyst 519insets could be a variety of different shapes and supports.Alternatively, the catalyst 519 can be an insert positioned verticallyacross the center of the channel inlets on a support such as a thin rod.This aspect is further described in FIG. 21 below.

FIG. 20 shows a fourth exemplary embodiment of a fuel processor 610 thatallows for counter-current flow of reactant and combustion gases whilehaving a non-linear arrangement of reformation reactors and vaporizers.Fuel processor 610 may be expanded in width, rather than length, toinclude more reformer sections and/or vaporizer sections as it is scaledup for more commercial applications. This embodiment differs from thatof FIG. 18 in that the reformer and vaporizer sections are each linear(rather than including a U-turn) and the entire processor is shown (notjust half of the processor). Generally, a square cross-section (to gasflow) is desired for minimal heat loss. Thus, the vaporizer/reformersection height is first increased, then the number of vaporizer/reformersections side-by-side (i.e. width), then the number ofvaporizer/reformer sections in series is increased.

Fuel processor 610 includes burner 611 which receives air from air inlet615 and gas from gas inlet 612 to produce hot combustion gas. The flowof hot combustion is directed to reformer sections 632, 636 by anoptional separator plate 608 gas and moves across reformer sections 632,636 in a direction away from burner 111. While combustion gas flows,reformer sections 632, 636 receive reformate at reformate inputs 620.Reformate flows counter-current to hot combustion gas towards reformateoutlets 628. Sample points 626 are located mid-way through reformersections 632, 636 to allow the progress of the underlying reformationreaction to be assessed. Put another way, the reformate outlets 628 areproximate the burner 611.

After flowing past reformer sections 632, 636, the hot combustion gasmakes a U-turn (indicated by arrow) and travels in the oppositedirection towards exhaust points 629. While combustion gas flows in theopposite direction, vaporizer sections 652, 654 receive water atvaporizer inlets 640. Water flows counter-current to the hot combustiongas towards the vaporizer outlets 648. Put another way, the vaporizerinlets are proximate the burner 611. After flowing past the vaporizersections, the hot combustion gas leaves fuel processor 610 at exhaustpoints 629.

FIG. 21 is a conceptual drawing of an exemplary embodiment of a catalystinsert 734 that could be used to place catalyst within a channel.Referring back to FIG. 19, this insert would be placed within thechannel defined by two separator shims and one channel shim.

The corrugated catalyst insert 734 includes a corrugated center piece730 that is coated on at least one side (and usually both) with catalyst731. The corrugated insert 734 is sandwiched between two flat shims 736.The inner surface 735 of each shim 736 is also illustrated as beingcoated with catalyst 731. This insert is then placed into the channel,with the outer surface 739 of each shim 736 contacting the sides of thechannel (not shown). Alternatively, the side shims 736 may be removed,and the catalyst insert may be only the corrugated center piece 730. Itis also contemplated, as previously noted, that catalyst could be coateddirectly upon the channel shim and separator shims that make up thechannel.

Catalyst-coated corrugated materials may be preferable due to open flowpassages yielding low pressure drop and good catalyst contacts. Thecorrugated catalyst insert 734 may be suitable for insertion intoreaction channels 134, 135, 138, 139 in the fuel processor 110 of FIG.5, or in the fuel processor 210 of FIG. 8 and the fuel processor 610 ofFIG. 20.

The various heat exchanger and fuel processor designs illustrated hereinare particularly useful for certain reactions which require a managedtemperature gradient to avoid “thermal shock”. For example, steamreforming of higher hydrocarbons is a reaction that is particularlysensitive to rapid heating (e.g. C₁₂H₂₆+12H₂O→12CO+25H₂). Contact withhot surfaces (needed for rapid heating) can cause cracking of thehydrocarbon molecule and deposition of carbon leading to deactivation ofthe catalyst and plugging of the channels in the reactor.Counter-current flow heats the steam/hydrocarbon mixture more gentlywith a lower temperature gradient (compared to co-current orcross-current flow type heat exchangers) until the reforming reaction isreasonably well underway. After some hydrogen and CO have been createdfrom the reforming reaction, carbon formation is less likely and theheating can continue at higher temperatures. The hydrocarbon/steammixture enters the reactor channel and is exposed to a relatively lowtemperature, and the temperature then increases through the length ofthe channel.

Another exemplary reaction where a managed temperature gradient isuseful is water-gas shift: CO+H₂O→CO₂+H₂. This reaction favors hydrogenproduction at low temperatures, but reaction rates are slow. The overallsize of the heat exchanger may be minimized in some cases by initiatingthe reaction at a high temperature and gradually reducing thetemperature as the reaction proceeds. In this case, the reactants enterone reactor channel at a high temperature, and temperature decreasesthrough the length of the channel, a coolant being used incounter-current flow to obtain the temperature gradient. Again, however,although counter-current flow is used in the figure to illustrate theoperation of the heat exchangers and reactors, co-current flow is alsocontemplated.

As previously stated, the heat exchangers of the present disclosure maybe made from the regular assembly of different shims that are punchedthrough, stacked in a regular pattern, and bonded. FIGS. 10-17illustrate different possible configurations for forming the heatexchangers by bonding. Bonding may be by diffusion bonding (a well-knownindustrial process) or brazing (also well known), with diffusion bondingbeing preferred for high temperature reactions. Another feature of theassemblies disclosed herein is that when diffusion bonding occurs, thereare no “unsupported bond areas”. The diffusion bonding process pressesthe shims together with significant force and at high temperature. Thecatalyst may be inserted into the reactor channels after bonding aspre-coated inserts, may be inserted either before bonding, or thecatalyst can be coated in-situ. Whether or not the catalyst can beinserted before bonding depends on the catalyst type and the bondingatmosphere. Generally, diffusion bonding temperature may be detrimentalto catalyst performance; hence, it may be advantageous to install thecatalyst after bonding.

As previously stated, longer channels are generally preferred, becausethey permit more gradual heating. However, practical limitations oncatalyst insertion or fabrication equipment size may limit the length ofa given channel. However, channels may be formed in series, sometimeswith an opportunity for inter-channel mixing between sets of channels.Thus, an effective length/width ratio can be any desired value withoutpractical limitation. For example, the channels 138, 139 in the fuelprocessor 110 of FIG. 5 can each be 3.5 inches long, and are connectedin series to each other through tubing. This configuration heats thefirst set of channels 138 to a relatively high temperature to performinitial reforming then introduces the partially reformed gas into thesecond set of channels 139 at relatively high temperature to completethe reforming reaction. This is essentially a parallel seriesconfiguration where the combustion path channels 133, 137 are parallelto the reaction channels 138, 139, but the reaction channels are inseries with each other. The embodiment of FIG. 5 has proven to beeffective and yields a more compact overall system configuration withlower overall heat loss, and additionally better efficiency.

The present disclosure has been described with reference to exemplaryembodiments. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the present disclosure be construed asincluding all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. A heat exchanger, comprising: a firstchannel having a flowpath, a first wall, a second wall opposite thefirst wall, an inlet manifold at a first end, and an outlet manifold ata second opposite end, the inlet manifold and the outlet manifoldrunning orthogonal to the flowpath; a second channel having a flowpathparallel to the flowpath of the first channel, the first channel and thesecond channel being separated by the first wall; and a fin extendingfrom the second channel into the first channel, the fin passing throughthe first wall and extending to the second wall; wherein the heatexchanger is formed from a channel shim and a separator shim, whereinthe channel shim defines the first channel, and wherein the separatorshim includes the fin; and wherein the channel shim and the separatorshim cooperate to form the first wall.
 2. The heat exchanger of claim 1,wherein the first channel has a plurality of micro-channels and thesecond channel has a plurality of micro-channels.
 3. The heat exchangerof claim 2, wherein the ratio of a first micro-channel width to a firstmicro-channel height is from 2:1 to 20:1.
 4. The heat exchanger of claim1, wherein the ratio of a channel shim height to a separator shim heightis from 0.125 to
 8. 5. The heat exchanger of claim 1, wherein thechannel shim comprises at least one micro-channel extending from a firstend of the channel shim to a second end of the channel shim.
 6. The heatexchanger of claim 5, wherein the micro-channel further comprises amixing manifold.
 7. The heat exchanger of claim 5, wherein the separatorshim further comprises slots that align with the micro-channel of thechannel shim.
 8. The heat exchanger of claim 5, wherein themicro-channel of the channel shim is formed from two longitudinal wallsjoined together by at least one transverse support, the micro-channelthus being separated into a series of chambers, wherein the chamber at afirst end of the micro-channel is shorter in length than the otherchambers.
 9. The heat exchanger of claim 1, wherein the channel shimfurther comprises alignment tabs on opposite corners.
 10. The heatexchanger of claim 1, wherein the channel shim further comprises notcheson opposite ends.
 11. The heat exchanger of claim 1, wherein theseparator shim further comprises a mixing manifold.
 12. The heatexchanger of claim 1, wherein the channel shim comprises: an entry endand a return end; two outer walls and a central wall that define twomicro-channels; and an alignment slot in the central wall.
 13. The heatexchanger of claim 1, wherein the separator shim comprises: an entry endand a return end; a central slot at the return end; two recesses at theentry end that align with the micro-channels of the channel shim; and analignment slot that aligns with the alignment slot of the channel shim.14. The heat exchanger of claim 1, wherein the reaction channel includesa catalyst.
 15. The heat exchanger of claim 14, wherein the catalyst isinserted into the reaction channel as a catalyst insert.
 16. The heatexchanger of claim 15, wherein the catalyst insert comprises acorrugated center piece coated on at least one side with the catalyst.17. The heat exchanger of claim 16, wherein the corrugated center pieceis sandwiched between two flat shims, and an inner surface of each flatshim is also coated with the catalyst.